Varnish Statistics One-liners

Varnish Command Line
 
Here are some useful examples of varnishtop and varnishlog at work.

Displays a continuously updated list of the most frequently requested URLs:
varnishtop -i RxURL
varnishlog -c | grep 'RxURL'

Top requests to your backend. This shows only the "TxURL", the URL being retrieved from your backend.
varnishtop -i TxURL
varnishlog -b | grep 'TxURL'

#See what cookies values are the most commonly sent to varnish.
varnishtop -i RxHeader -I Cookie
varnishlog -c | grep 'Cookie: '

#Which host is being requested the most. Only really useful when you're serving multiple hosts in Varnish.
varnishtop -i RxHeader -I '^Host:'
varnishlog -i RxHeader | grep 'Host: '

#Accept-Encoding will show the most popular Accept-Encoding header the client are sending you.
varnishtop -i RxHeader -I

See what useragents are the most common from the clients
varnishtop -i RxHeader -C -I ^User-Agent

See what user agents are commonly accessing the backend servers, compare to the previous one to find clients that are commonly causing misses.
varnishtop -i TxHeader -C -I ^User-Agent

See what accept-charsets are used by clients
varnishtop -i RxHeader -I '^Accept-Charset

Listing all details about requests resulting in a 500/404 status:
varnishlog -b -m "RxStatus:500"
varnishlog -b -m "RxStatus:404"







References

• http://book.varnish-software.com/3.0/Getting_started.html
• https://www.varnish-cache.org/docs/3.0/reference/varnishlog.html
• https://www.varnish-cache.org/docs/3.0/reference/varnishtop.html
• https://www.varnish-cache.org/docs/3.0/tutorial/increasing_your_hitrate.html
• https://www.varnish-cache.org/docs/3.0/tutorial/logging.html#tutorial-logging
• https://ma.ttias.be/useful-varnish-3-0-commands-one-liners-with-varnishtop-and-varnishlog/
• http://stackoverflow.com/questions/13247707/how-to-read-output-of-varnishtop
• http://www.eldefors.com/varnish-command-line-tools/
• https://www.varnish-cache.org/trac/wiki/

Request Entity Too Large Solution

Stumbled across this issue of request entity too large when trying a script on server is trying to upload large files.  This referrers to  Apache/NGINX/IIS servers running PHP.


The solution seems to lie in the change the following variables.

memory_limit =128M
post_max_size = 96M
upload_max_filesize = 64M

Test and increase the above variables slowly by 16/32M increments to ensure your web hosting can handled

If you are on NGINX you will need to adjust client_max_body_size in the http block of the config file

The error,  '413 Request Entity Too Large'.

http {
    #...
        client_max_body_size 128m;
    #...
}


Note 'post_max_size integer' sets max size of post data allowed. This setting also affects file upload. To upload large files, this value must be larger than 'upload_max_filesize'. Generally speaking, 'memory_limit' should be larger than 'post_max_size'.

You might also want to increase the max-execution-time. Note however you server configurations, i.e. timeouts, might interrupt executions.

Varnish and SEO

Varnish is a a great caching solution but it can do more. With Search Engine Optimisation it is always recommended that you have one base URL,often referred to as a Canonical URL,  either www.mysample or mysample domain. Some website owners even have multiple domains. The snippets below show how you can redirect www/non-www to non-www/www and or multiple domains to a Canonical URL.

Varnish 3
in sub vcl_recv add close to the top

    if (req.http.host == "www.mysample.com" || req.http.host == "my-sample.com" || req.http.host == "www.my-sample.com") {
        set req.http.host = "mysample.com";
        error 750 "http://" + req.http.host + req.url;
    }

in sub vcl_error add
   if (obj.status == 750) {

        set obj.http.Location = obj.response;
        set obj.status = 301;
        return(deliver);
    }

Varnish 4
in sub vcl_recv add

    if (req.http.host ~ "^www.mysample.com") {
        return (synth (750, ""));
    }

in sub vcl_synth

    if (resp.status == 750) {
        set resp.status = 301;
        set resp.http.Location = "http://mysampele.com" + req.url;
        return(deliver);
    }

Actually I like the implementation in Varnish 4 better. As you can make all the related changes at one place instead at 2 locations in Varnish 4. This also helps improving your memory used as only a single option is stored in cache instead of one for www.mysample.com/index.html and another for mysample.com/index.html

Hope this helps someone

Source
How to redirect non-www URLs to www in Varnish